龙门山断裂带断层泥中速—高速摩擦性质的实验研究

发布时间：2018-01-09 07:40

本文关键词：龙门山断裂带断层泥中速—高速摩擦性质的实验研究　出处：《中国地震局地质研究所》2013年博士论文　论文类型：学位论文

【摘要】：为了认识龙门山断裂带在汶川地震中的同震滑动力学性质，我们对龙门山断裂带地表断层带露头上的断层泥及少量WFSD-1断层泥开展了中速-高速摩擦实验研究。主要关注的问题包括：龙门山断裂带高速摩擦性质及其不均匀性、震后断层强度恢复问题、高速滑动可能的主导弱化机制问题和宽速度域内摩擦滑动速度依赖性问题。基于对断层带结构和断层岩样品的精细分析，我们从矿坪子和八角庙断层带露头采集了四种断层泥样品。对这些样品及另外三种WFSD-1样品开展的高速摩擦实验揭示除了矿坪子露头黑色断层泥，其他几种断层泥的高速摩擦性状均表现为负指数衰减型滑动弱化。矿坪子露头黑色断层泥具有非常独特的力学性状：初始阶段快速的滑移弱化，接着出现微弱的滑移强化至第二个峰值，之后逐渐弱化至稳态。微结构观察和对比实验表明初始快速弱化和之后的微弱强化主要是黑色断层泥特殊的微结构演化造成的。基于经验公式和进一步的推导，我们选取了六个能够描述稳态摩擦系数、滑动弱化距离和比破裂能对速率和正应力依赖性的本构参数。我们对本论文和前人研究过的四个露头共计六种断层泥的高速摩擦性质进行了比较，从这上述六个本构参数的定量化比较来看，龙门山断裂带高速摩擦性质的不均匀性是存在的。不过，如果仅仅是考察摩擦强度，高速滑移下的稳态摩擦系数在整个断层带上的均匀性还是相当高的；如干燥条件下速率等于1.4m/s时几乎均小于0.2，在含水条件下还将更低。这些断层泥在高速滑移下显著的滑移弱化必定在汶川地震中极大地促进了破裂的传播，也能够解释震后钻探观测到的温度异常较小的现象。高速滑移下的slide-hold-slide实验揭示断层在经历高速滑移显著滑移弱化之后，能够在5~10s内快速恢复大部分的强度(摩擦系数增加约0.4)，愈合率(摩擦系数增量与保持时间对数的比值)达0.154~0.188；之后是跟时间对数成正比的缓慢愈合，愈合率约0.015~0.016。温度计算表明初始快速的强度恢复和温度的快速降低有关。5~10s的强度恢复时间尺度小于一般大地震的上升时间，从而支持自愈合滑动脉冲式的地震破裂模式。同时，断层高速滑移之后快速的强度恢复对稳定断层的摩擦滑动、减少余震也可能起到了重要作用。对极薄(0.1~0.14mm)和常规厚度断层泥(1.0~1.4mm)开展的中速-高速摩擦对比实验揭示薄层断层泥的剪切滑移能够更快地弱化断层，而且断层显著滑动弱化的特征滑动速率也低得多；微结构观察表明这可能是凹凸体急剧加热弱化机制在薄层断层泥实验中更加显著造成的；极薄和较厚断层泥高速摩擦性状的差异可能暗示着野外断层上相对更薄的断层泥层能够更快地在同震滑移中弱化断层、也能更大程度地促进地震破裂的传播。利用辉长岩和黄铜作围岩开展的高速摩擦对比实验揭示黄铜作围岩的实验中仅观察到微弱的滑动弱化，温度计算表明这与黄铜的高热导抑制了断层带的急剧升温有关，这暗示了凹凸体急剧加热弱化和热压作用这两种跟摩擦生热相关的机制对断层弱化的重要性。利用黄铜作围岩对纳米氧化镁开展的高速摩擦实验表明，在升温受抑制的情况下，即使是纯纳米颗粒物质也不能有效地显著弱化断层；这一结果表明纳米颗粒的滚动润滑机制不是断层高速滑动弱化的主要机制。对断层泥从低速到高速开展的摩擦实验研究表明，中等速率域内显著的速度强化是有可能存在的。但是实验同时揭示数百μm/s以下的摩擦滑动在大剪切应变下(如,1000)存在显著的应变硬化(滑移强化)，这可能与断层泥在大应变下发生的物质和结构上的改变有关，今后对宽速度域内摩擦滑动速度依赖性进行研究时，，需要充分考虑应变硬化带来的影响。
[Abstract]:In order to bring the coseismic slip properties in Wenchuan earthquake in the Longmen Mountain Fault Zone understanding, outcrop on the fault gouge of mud and a small amount of WFSD-1 we surface faults of Longmen mountain fracture experiment of high-speed friction speed. The main concern include: uneven and high speed friction properties of the Longmen Mountain Fault Zone, the problem after the earthquake fault recovery strength, leading high-speed sliding possible Weakening Mechanism Problems and wide speed domain sliding speed dependent problem.
Fine analysis of fault zone structure and fault rock samples based on us from the mine and the octagonal Temple Ping Zi fault outcrop collected four species of fault gouge samples. These samples and other three samples to carry out the high speed friction experiment of WFSD-1 revealed in addition to mine Ping Zi outcrop black gouge, which he gouge several high-speed friction sliding type traits showed that the exponential decay weakened. Ore Ping Zi black gouge with outcrop mechanical properties is very unique: slip weakening fast initial stage, then the weak slip to strengthen the second peak, then gradually weakened to a steady state. The micro structure observation and experiments show that after the initial rapid weakening and strengthening weak the black gouge is mainly caused by the special micro structure evolution. And further deduced based on empirical formula, we selected six to describe the steady friction coefficient, sliding weak The distance and the rupture rate and is the ratio of the stress dependence of the constitutive parameters. In this paper we four outcrop and previous research had a total of six kinds of fault gouge and high speed friction properties were compared, from the comparison of the six constitutive parameters of quantification, inhomogeneity of high-speed friction properties the Longmen mountain fault zone is there. However, if only to study friction strength, steady friction coefficient of sliding speed is quite high in the uniformity of the whole fault zone on the dry conditions; such as the 1.4m/s rate is equal to almost all less than 0.2, under Hydrous conditions will also lower. The fault gouge slip significantly in high speed slip weakening in the earthquake in Wenchuan will greatly promote the propagation of the rupture, can also explain the abnormal temperature smaller after drilling of the observed phenomenon.
Slide-hold-slide experiment of high speed of sliding fault after weakening speed revealed significant slip slip, can quickly restore most of the strength in 5~10s (friction coefficient increased about 0.4), the healing rate (the ratio of friction coefficient increment and keep the logarithm of time) of 0.154~ 0.188; followed with time is proportional to the logarithm of the slow healing, healing rate about 0.015~0.016. temperature calculation showed that the initial rapid recovery and the rapid decrease of temperature strength on.5~10s strength recovery time scale is less than the rise time of the earthquake, so as to support the self-healing slip pulse type earthquake rupture model. At the same time, the rapid recovery of strength of sliding friction stability after fault fault slip speed, reduce the aftershocks may played an important role.
The thin thickness (0.1~0.14mm) and conventional fault gouge (1.0~1.4mm) carry out medium - speed friction experiments reveal the shear slip fault gouge layer can be rapidly weakening fault slip rate and characteristics of fault slip weakening was much lower; micro structure observation show that the asperity may be more significant weakening mechanism of rapid heating result in thin gouge experiment; thin and thick difference gouge high-speed friction traits suggests that fault gouge layer field relatively thinner faster in the coseismic slip of weak fault, can greatly promote the spread of earthquake rupture. By contrast experiment of high-speed gabbro and brass the friction surrounding rock revealed brass experiments were observed only in the weak slip weakening, temperature calculation shows that high thermal conductivity and the sharp brass suppression of the fault zone The temperature, suggesting that the asperity rapid heating and hot pressing the weakening effect of these two related to friction mechanism of the importance of fault weakening. Using brass rock on high speed friction experiment of nano Magnesium Oxide carried out shows that during the heating by inhibiting the case, even the pure nano particles can effectively weaken significantly fault the results show that the main mechanism; the weakening of rolling lubrication mechanism of nano particles is not fault high-speed sliding.
Study on friction experiment of fault gouge from low speed to high speed development, the medium rate domain significantly enhanced speed is possible. But the experiments also revealed hundreds of m/s friction in the sliding shear strain (e.g., 1000) there is significant strain hardening (slip strengthening), material and structure a possible fault gouge under large strain on the change, the future of wide speed domain sliding speed dependent study, need to fully consider the influence of strain hardening brings.

【学位授予单位】：中国地震局地质研究所
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU45;P315

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